1. Field of the Invention.
The present invention relates to torque indicating apparatus and methods, and more particularly, but not by way of limitation, to apparatus and methods for verifying that an amount of torque applied to a threaded fastener is equal to or greater than a predetermined torque value.
2. Description of the Prior Art.
Wheel loss is a major cause of automobile accidents throughout the world. The loss of a wheel during operation of an automobile can cause the automobile to veer off the road or into oncoming traffic. Although the loss of a wheel can be caused by many factors, it is most commonly caused by the failure of mechanics to sufficiently tighten the wheel onto the wheel hub of the automobile. Due to the growing number of tire and brake repair and replacement specialty shops, this problem is getting worse instead of better.
When replacing or repairing tires and brakes, the typical mechanic will remove all four of the wheels from the wheel hubs of the automobile at the same time. After the new tires are mounted on the wheels or the other work is performed, the mechanic will position all of the wheels back on the wheel hubs before any lug nuts are threaded onto the lug studs. Once all of the wheels are positioned back on the wheel hubs, the mechanic will thread the lug nuts onto the lug studs and tighten the lug nuts with an impact wrench. Most mechanics rely on feel to make sure that the amount of torque applied to the lug nuts equals or exceeds a proper torque value.
Due to the number of tires that a tire and/or brake mechanic removes and replaces each day, it is easy for the mechanic to forget to tighten one or more of the lug nuts after the lug nuts are threaded onto the lug studs. Unfortunately, once the lug nuts are threaded onto the lug studs, it is hard to visually determine if they have been tightened. Even if the mechanic remembers to tighten all of the lug nuts, the lug nuts are not always tightened sufficiently. The mechanic's feeling as to the magnitude of the torque applied to the lug nuts may not accurately verify that the lug nuts have been sufficiently tightened. If the threads of the lug nut or lug stud are worn or stripped, the mechanic may think that the lug nuts have been sufficiently tightened when in fact they have not.
Due to the time and trouble involved, most tire and/or brake mechanics do not use a torque wrench or similar torque indicating apparatus to make sure that the lug nuts have been sufficiently tightened. Furthermore, as with the mechanic's own feeling, the indication provided by torque wrenches and similar torque indicating apparatus may not be accurate. If the threads of the lug stud or lug nut are worn or stripped, the torque wrench or other apparatus may indicate that the lug nuts have been sufficiently tightened when in fact they have not.
If one or more of the lug nuts are not sufficiently tightened, the wheel may rotate out of alignment. This can put excessive stress on and result in failure of one of more of the lug studs and/or the wheel hub, which can ultimately result in loss of the wheel. Thus, failure to apply a sufficient amount of torque to just one lug nut can result in the wheel eventually falling off.
There is a need for a reliable means to remind mechanics to tighten each lug nut and to verify that the lug nuts have been tightened sufficiently.